Restart DB Cluster restarts only one PXC server and one proxySQL, not all of them

Impact on the user:

• user will not get what they've tried to achieve by restarting the DB Cluster

Steps to reproduce:

1. Setup PXC cluster in PMM
2. wait it's ready
3. Restart it
4. Wait it's restarted
5. check status in k8s

Actual result:
spronin-test-proxysql-0 3/3 Running 6 13h spronin-test-proxysql-1 3/3 Running 0 13h spronin-test-proxysql-2 0/3 ContainerCreating 0 1s spronin-test-pxc-0 1/1 Running 0 13h spronin-test-pxc-1 1/1 Running 8 13h spronin-test-pxc-2 1/1 Terminating 0 2m29s

as you can see only one PXC and one proxySQL pod's started recently, others are 13h Up

Expected Result:
All pods have recent uptime

Workaround:
restart pods from kubectl

Suggested Implementation:

• When dbaas-controller gets Restart request
• Pause DB cluster
• Wait until DB cluster is paused
  • Start new goroutine to Resume DB cluster
• Return response

Possible issues:

• If dbaas-controller restarts during restart DB cluster may stuck in pause state
• After pausing DB cluster it may have active status for a few seconds (PMM-7397) 

Details:

PMM-6824 implemented database cluster restart with kubectl rollout restart. It is good enough for alpha, but not good enough for beta: we can lose data this way, and operators' team confirmed it is not safe.

For beta1, we should implement restart via full cluster pause/resume: https://www.percona.com/doc/kubernetes-operator-for-pxc/pause.html

The same functionality will be available for PSMDB.